Great question — answering as the UphillTech team:
No, the glaze will make very little difference. Jam is 60% sugar and sugar is an excellent preservative. To put it another way: if you find jam keeps well in the pot, the same should hold once it's on the cake.
Full answer by Mark Wildon: https://cooking.stackexchange.com/a/95173 (CC BY-SA 4.0).
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